High density polyurethane and polyisocyanurate construction boards and composite boards

ABSTRACT

A covered roof includes a roof deck, an insulation board, and a coverboard. The insulation board includes a polyurethane, a polyisocyanurate, or a mix of polyurethane and polyisocyanurate cellular structure, has a density that is less than 2.5 pounds per cubic foot, and has a first planar surface and a second planar surface, each having a facer positioned adjacent thereto. The coverboard includes a polyurethane, a polyisocyanurate, or a mix of polyurethane and polyisocyanurate cellular structure, has a density greater than about 2.5 pounds per cubic foot and less than 6 pounds per cubic foot, an iso index of at least 175, and a first planar surface and a second planar surface, each having a facer positioned adjacent thereto.

This application is a continuation of U.S. Non-Provisional applicationSer. No. 13/414,054, filed on Mar. 7, 2012 is a continuation of U.S.Non-Provisional application Ser. No. 13/108,060, filed May 16, 2011,which is a continuation application of U.S. Non-Provisional applicationSer. No. 11/343,466, filed Jan. 30, 2006, which gains the benefit ofU.S. Provisional Application No. 60/649,385, filed Feb. 1, 2005, and isalso a continuation of U.S. Non-Provisional application Ser. No.13/417,408, which is a U.S. Non-Provisional application Ser. No.13/108,053, filed May 16, 2011, which is a continuation of U.S.Non-Provisional application Ser. No. 11/343,466, which gains the benefitof U.S. Provisional Application No. 60/649,385, filed Feb. 1, 2005 allof which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is directed toward high density polyurethane orpolyisocyanurate construction boards and composite boards, as well astheir use in flat or low-slope roofing systems.

BACKGROUND OF THE INVENTION

Flat or low-slope roofs are often covered with multi-layered roofingsystems. These roofing systems often include a roof deck, an insulationlayer, and a protective, weather-resistant membrane. In some situations,a coverboard is also employed. In many situations, insulation boards aretypically adhered directly to a roof deck, which is most commonlyconstructed of concrete or steel. These insulation boards are typicallyclosed-cell foams that include polyurethane or polyisocyanurate cellularmaterials with an insulating gas trapped within the cells. Theinsulation boards are then covered with the weather resistant membrane.

The foam insulation boards are typically low density cellularstructures. The low density stems from two primary considerations. Thefirst is cost because lower density cellular structures employ lessmaterial. Also, and often more important, the insulation value of theboard can be improved with lower density structures. While a density ofzero would be ideal (i.e., a vacuum), a certain degree of cellularstructure—which gives rise to the density—is required to maintain theintegrity of the insulation boards. Particularly, a foam core density ofgreater than about 1.5 pounds per cubic foot (pcf) is needed to maintainstrength, and a core density of less than about 2 pcf is conventionalfor cost and insulation considerations.

Coverboards typically include fiber boards, gypsum products such asdensdeck, and perlite boards. Coverboards are typically used to addintegrity to the roof. For example, especially where improved fireperformance is sought, the coverboard may first be applied to the steeldeck, the insulation board is applied on top of the coverboard, and themembrane is then applied over the insulation board. Alternatively,especially where the roof may experience heavy traffic, the insulationboard may be applied to the roof deck, the coverboard applied over theinsulation board, and then the membrane is applied over the coverboard.In the latter situation, the coverboard obviously provides protection tothe insulation board, which is prone to denting or damage due to thefact that the insulation boards are low density cellular materials.

Coverboards are also extensively used in re-roofing situations. In theseapplications, the coverboard may be referred to as a “re-coverboard.” Aswith residential roofs, flat or low-slope roofs can be re-roofed withoutremoving or “tearing off” the existing roofing membrane. In manyinstances, the re-coverboard is first applied to the existing roofingmembrane before a new roofing membrane is applied to the roof. Also, anadditional layer of insulation board can be applied before the newmembrane is applied. Depending upon the result desired, there-coverboard can be applied above or below the insulation board.

In other instances, a composite board is employed in lieu of (orpossible in addition to) the coverboard and insulation board. Thecomposite boards include an insulation layer together with a layer thatis rather robust such as a wood fiber, gypsum, or perlite board. Oneadvantage of the composite board is the ease of installation. In otherwords, rather than apply both an insulation board and a coverboard, thecomposite board can simply be installed in a one-step process. Otheradvantages have been observed based upon the fact that the compositeboard is formed integrally within a controlled environment (i.e., thefactory).

The use of construction boards in new roofing systems and re-roofsituations is, therefore, technologically important therebynecessitating further advancement in the field.

SUMMARY OF THE INVENTION

In general the present invention provides a covered low-slope or flatroof comprising (a) a roof deck, (b) an insulation board including apolyurethane or polyisocyanurate cellular structure having a densitythat is less than 2.5 pounds per cubic foot, (c) a coverboard includinga polyurethane or polyisocyanurate cellular structure having a densitygreater than about 2.5 pounds per cubic foot, and (d) a membrane.

The present invention also includes a method of re-roofing a low-slopeor flat roof, the method comprising (a) applying a re-coverboard to anexisting covered low-slope or flat roof, wherein the re-coverboardincludes a polyurethane or polyisocyanurate cellular structure having adensity that is greater than about 2.5 pounds per cubic, and (b)applying a membrane to the re-coverboard subsequent to the step ofapplying a re-coverboard.

The present invention further includes a composite board comprising (I)a planar structure including (a) a first layer comprising a polyurethaneor polyisocyanurate cellular structure having a density that is lessthan about 2.5 pounds per cubic foot, and (b) a second layer comprisinga polyurethane or polyisocyanurate cellular structure having a densitythat is greater than about 2.5 pounds per cubic foot.

The present invention also includes a composite board comprising a leastone low density layer comprising a polyurethane or polyisocyanuratecellular structure having a density that is less than about 2.5 poundsper cubic foot, and a least one high density layer comprising apolyurethane or polyisocyanurate cellular structure having a densitythat is greater than about 2.5 pounds per cubic foot.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of a high-density constructionboard of the present invention.

FIG. 1A is a fragmentary perspective view of another high-densityconstruction board of the present invention.

FIG. 2 is a fragmentary perspective view of a roofing system including ahigh density coverboard.

FIG. 3 is a fragmentary perspective view of a roofing system including ahigh density coverboard.

FIG. 4 is a fragmentary perspective view of a roofing system includingre-roof layers.

FIG. 5 is a fragmentary perspective view of a roofing system includingre-roof layers.

FIG. 6 is a fragmentary perspective view of a composite constructionboard of the present invention.

FIG. 6A is a fragmentary perspective view of another compositeconstruction board of the present invention.

FIG. 6B is a fragmentary perspective view of still another compositeconstruction board of the present invention.

FIG. 6C is a fragmentary perspective view of still yet another compositeconstruction board of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

One or more embodiments of the present invention are directed toward ahigh density polyurethane or polyisocyanurate cellular constructionboard. The unique high density characteristics of these boards allowthem to be advantageously used in the construction of new flat orlow-sloped roofs, as well as in re-roofing situations. In other words,these construction boards are useful as coverboards or re-coverboards.

A high density board according to one or more embodiments is depicted inFIG. 1. Board 10 includes a cellular body 11 having a planar shape withfirst planar surface 12 and second planar surface 14, each defined by alength 16 and a width 18. Board 10 may also be characterized by athickness 20. Length 16 and width 18 of board 10 may vary, and theseembodiments are not necessarily limited by the selection of a particularlength or width. Nonetheless, because these boards are advantageouslyemployed in the construction industry, board 10 may be sized to a 4′×8′sheet (e.g., 3.75°×7.75°), a 4′×10′ sheet, or a 4′×4′ sheet. The width20 of the board can generally be greater than about 0.5 inches, and maybe from about 0.5 to 4.5 inches or in other embodiments from about 1.0to 4.0 inches in thickness.

Board 10 may include an optional facer 22, which can be positionedadjacent one of the first or second planar surfaces 12 or 14. Forexample, as shown in FIG. 1, facer 22 may be positioned adjacent secondplaner surface 14. In one or more embodiments, facer 22 can be integralwith planar surface to which it is adjacent as a result of the methodsemployed to manufacture board 10, which will be disclosed below.

Facer 22 may include a variety of materials or compositions, many ofwhich are known or conventional in the art. Useful facers include thosecomprising aluminum foil, cellulosic fibers, reinforced cellulosicfibers, craft paper, coated glass fiber mats, uncoated glass fiber mats,chopped glass, and combinations thereof. Useful facer materials areknown as described in U.S. Pat. Nos. 6,774,071, 6,355,701, RE 36674,U.S. Pat. Nos. 6,044,604, and 5,891,563, which are incorporated hereinby reference. The thickness of the facer material may vary; for example,it may be from about 0.01 to about 1.00 or in other embodiments fromabout 0.015 to about 0.050 inches thick. The facer materials can alsoinclude more robust or rigid materials such as fiber board, perliteboard, or gypsum board. The thickness of the rigid facer can vary; forexample, the thickness of the rigid facer can be from about 0.2 to about1.5 inches, or in other embodiments from about 0.25 to about 1.0 inches.

As shown in FIG. 1A, board 10 may also optionally include a facer 23positioned adjacent the planer surface opposite the planar surface onwhich facer 22 is positioned. For example, facer 22 is positionedadjacent second planer surface 14, and facer 23 is positioned adjacentfirst planer surface 12. Facer 23 can include the same or differentmaterials or compositions, as well as the same or different thickness asfacer 22.

Also, as noted above, facers 22 and 23 are optional. Therefore, in oneor more embodiments, board 10 may be facerless. The ability to producefacerless construction boards is known as described in U.S. Pat. No.6,117,375, which is incorporated herein by reference.

Body 11 includes a polyurethane or polyisocyanurate cellular structure,which refers to an interconnected network of solid struts or plates thatform the edges and faces of cells. These cellular structures may, in oneor more embodiments, also be defined by a “relative density” that isless than about 0.8, in other embodiments less than 0.5, and in otherembodiments less than 0.3. As those skilled in the art will appreciate,“relative density” refers to the density of the cellular materialdivided by that of the solid from which the cell walls are made. As therelative density increases, the cell walls thicken and the pore spaceshrinks such that at some point there is a transition from a cellularstructure to one that is better defined as a solid containing isolatedpores.

Despite the cellular nature of body 11, it has a high density. In one ormore embodiments, the density of body 11 is greater than 2.5 pounds percubic foot, as determined according to ASTM C303, in other embodimentsthe density is greater than 2.8 pounds per cubic foot, in otherembodiments greater than 3.0 pounds per cubic foot, and still in otherembodiments greater than 3.5 pounds per cubic foot; on the other hand,in one or more embodiments, the density of body 11 may be less than 20pounds per cubic foot, in other embodiments less than 10 pounds percubic foot, and still in other embodiments less than 6 pounds per cubicfoot.

The boards of one or more embodiments of this invention can bemanufactured by using known techniques for producing polyurethane orpolyisocyanurate insulation boards except the formulation may need to bemodified, and the hydraulic clamping pressure of the laminator may needto be adjusted. Furthermore, the amount of total blowing agent (forexample, carbon dioxide from the reaction of isocyanates with isocyanatereactive compounds such as water plus a physical blowing agent) may needto be decreased. Likewise, the amount of catalysts may also need to bedecreased. The higher density and potentially higher foam expansionpressure may necessitate higher hydraulic clamping pressure to maintainuniform board thickness and to move the product down the laminator.

In general, processes for the manufacture of polyurethane orpolyisocyanurate insulation boards are known in the art as described inU.S. Pat. Nos. 6,117,375, 6,044,604, 5,891,563, 5,573,092, U.S.Publication Nos. 2004/01099832003/0082365, 2003/0153656, 2003/0032351,and 2002/0013379, as well as U.S. Ser. Nos. 10/640,895, 10/925,654, and10/632,343, which are incorporated herein by reference.

In general, and in a manner that is conventional in the art, the boardsof the present invention may be produced by developing or forming apolyurethane and/or polyisocyanurate foam in the presence of a blowingagent. The foam may be prepared by contacting an A-side stream ofreagents with a B-side stream of reagents and depositing the mixture ordeveloping foam onto a laminator. As is conventional in the art, theA-side stream includes an isocyanate and the B-side includes anisocyanate-reactive compound.

The A-side stream typically only contains the isocyanate, but, inaddition to isocyanate components, the A-side stream may containflame-retardants, surfactants, blowing agents and othernon-isocyanate-reactive components.

Suitable isocyanates are generally known in the art. Useful isocyanatesinclude aromatic polyisocyanates such as diphenyl methane, diisocyanatein the form of its 2,4′-, 2,2′-, and 4,4′-isomers and mixtures thereof,the mixtures of diphenyl methane diisocyanates (MDI) and oligomersthereof known in the art as “crude” or polymeric MDI having anisocyanate functionality of greater than 2, toluene diisocyanate in theform of its 2,4′ and 2,6′-isomers and mixtures thereof, 1,5-naphthalenediisocyanate, and 1,4′ diisocyanatobenzene. Exemplary isocyanatecomponents include polymeric Rubinate 1850 (Huntsmen Polyurethanes),polymeric Lupranate M70R (BASF), and polymeric Mondur 489N (Bayer).

The B-side stream, which contains isocyanate reactive compounds, mayalso include flame retardants, catalysts, emulsifiers/solubilizers,surfactants, blowing agents, fillers, fungicides, anti-staticsubstances, water and other ingredients that are conventional in theart.

An exemplary isocyanate-reactive component is a polyol. The terms polyolor polyol component include diols, polyols, and glycols, which maycontain water as generally known in the art. Primary and secondaryamines are suitable, as are polyether polyols and polyester polyols.Useful polyester polyols include phthalic anhydride based PS-2352(Stepen), phthalic anhydride based polyol PS-2412 (Stepen), teraphthalicbased polyol 3522 (Kosa), and a blended polyol TR 564 (Oxid). Usefulpolyether polyols include those based on sucrose, glycerin, and toluenediamine. Examples of glycols include diethylene glycol, dipropyleneglycol, and ethylene glycol. Suitable primary and secondary aminesinclude, without limitation, ethylene diamine, and diethanolamine. Inone embodiment a polyester polyol is employed. In one or moreembodiments, the present invention may be practiced in the appreciableabsence of any polyether polyol. In certain embodiments, the ingredientsare devoid of polyether polyols.

Catalysts are believed to initiate the polymerization reaction betweenthe isocyanate and the polyol, as well as a trimerization reactionbetween free isocyanate groups when polyisocyanurate foam is desired.While some catalysts expedite both reactions, two or more catalysts maybe employed to achieve both reactions. Useful catalysts include salts ofalkali metals and carboxylic acids or phenols, such as, for examplepotassium octoate; mononuclear or polynuclear Mannich bases ofcondensable phenols, oxo-compounds, and secondary amines, which areoptionally substituted with alkyl groups, aryl groups, or aralkylgroups; tertiary amines, such as pentamethyldiethylene triamine(PMDETA), 2,4,6-tris[(dimethylamino)methyl]phenol, triethyl amine,tributyl amine, N-methyl morpholine, and N-ethyl morpholine; basicnitrogen compounds, such as tetra alkyl ammonium hydroxides, alkalimetal hydroxides, alkali metal phenolates, and alkali metal acholates;and organic metal compounds, such as tin(II)-salts of carboxylic acids,tin(IV)-compounds, and organo lead compounds, such as lead naphthenateand lead octoate.

Surfactants, emulsifiers, and/or solubilizers may also be employed inthe production of polyurethane and polyisocyanurate foams in order toincrease the compatibility of the blowing agents with the isocyanate andpolyol components.

Surfactants may serve two purposes. First, they may help toemulsify/solubilize all the components so that they react completely.Second, they may promote cell nucleation and cell stabilization.Exemplary surfactants include silicone co-polymers or organic polymersbonded to a silicone polymer. Although surfactants can serve bothfunctions, a more cost effective method to ensureemulsification/solubilization may be to use enoughemulsifiers/solubilizers to maintain emulsification/solubilization and aminimal amount of the surfactant to obtain good cell nucleation and cellstabilization. Examples of surfactants include Pelron surfactant 9920,Goldschmidt surfactant B8522, and GE 6912. U.S. Pat. Nos. 5,686,499 and5,837,742 are incorporated herein by reference to show various usefulsurfactants.

Suitable emulsifiers/solubilizers include DABCO Kitane 20AS (AirProducts), and Tergitol NP-9 (nonylphenol+9 moles ethylene oxide).

Flame Retardants may be used in the production of polyurethane andpolyisocyanurate foams, especially when the foams contain flammableblowing agents such as pentane isomers. Useful flame retardants includetri(monochloropropyl)phosphate, tri-2-chloroethyl phosphate, phosphonicacid, methyl ester, dimethyl ester, and diethyl ester. U.S. Pat. No.5,182,309 is incorporated herein by reference to show useful blowingagents.

Useful blowing agents include isopentane, n-pentane, cyclopentane,alkanes, (cyclo) alkanes, hydrofluorocarbons, hydrochlorofluorocarbons,fluorocarbons, fluorinated ethers, alkenes, alkynes, carbon dioxide, andnoble gases. Depending on the required density of the board, the amountof blowing agent may need to be decreased up to about 95% from astandard formulation. The amount of water may also, optimally, bereduced. The less blowing agent used, the less catalyst is generallyused.

As noted above, the high density polyurethane or polyisocyanurate boardsof this invention may be employed in the construction of new roofingstructures and thereby form a unique flat or low-slope roofing system.For example, FIGS. 2 and 3, respectively, show unique roofing systems 30and 31 that employ high density board 10. Furthermore, although the highdensity board 10 depicted in FIGS. 2 and 3 does not include facers,facers can be used.

As shown in FIG. 2, roofing system 30 includes a roof deck 32 havinginsulation board 34 disposed thereon, high density board 10 positionedon optional insulation board 34, and a water-protective layer ormembrane 36 disposed on top of high density board 10. In an alternateembodiment, as shown in FIG. 3, roofing system 31 includes roof deck 32with high density board 10 disposed thereon. Insulation board 34 ispositioned on high density board 10, and water protective layer ormembrane 36 is disposed on top of optional insulation board 34.

The particular embodiment shown in FIG. 2 is advantageous on roofs thatexperience high traffic and/or heavy loads. High density board 10 can befairly robust and durable, and therefore protects insulation board 34from damage. As those skilled in the art will appreciate, thelow-density nature of insulation board 34 makes it susceptible todamage, particularly through denting, when it is mechanically impingedsuch as by pedestrian or vehicle traffic, or by objects falling andcontacting the roof. Also, the embodiment shown in FIG. 2 mayadvantageously reduce flame propagation in exterior fire tests such asUL 790 or ASTM E108.

Practice of this invention is not limited by the selection of anyparticular roof deck. Accordingly, the roofing systems of thisembodiment, as shown in FIGS. 2 and 3, can include a variety of roofdecks. Exemplary roof decks include concrete pads, steel decks, woodbeams, and foamed concrete decks.

Practice of this invention is likewise not limited by the selection ofany particular insulation board. As is known in the art, severalinsulation materials can be employed. In one embodiment, the insulationboard comprises polyurethane or polyisocyanurate cellular material.These insulation boards are known in the art as disclosed in U.S. Pat.Nos. 6,117,375, 6,044,604, 5,891,563, 5,573,092, U.S. Publication Nos.2004/01099832003/0082365, 2003/0153656, 2003/0032351, and 2002/0013379,as well as U.S. Ser. Nos. 10/640,895, 10/925,654, and 10/632,343, whichare incorporated herein by reference. In general, polyurethane ischaracterized by having an index of from about 100 to about 120;polyisocyanurate is generally characterized by having an index that isin excess of 150 (in other embodiments at least 175, and in otherembodiments at least 200; and insulation with an index between 120 and150 generally includes a mix of polyurethane and polyisocyanurate.

In those embodiments where the insulation layer comprises polyurethaneor polyisocyanurate cellular material, these cellular materials aredefined by a foam density (ASTM C303) that is less than 2.5 pounds percubic foot, in other embodiments less than 2.0 pounds per cubic foot, inother embodiments less than 1.9 pounds per cubic foot, and still inother embodiments less than 1.8 pounds per cubic foot. In one or moreembodiments, these polyurethane or polyisocyanurate insulation layersare likewise characterized by having a density that is greater than 1.50pounds per cubic foot and optionally greater than 1.55 pounds per cubicfoot.

Practice of this invention is likewise not limited by the selection ofany water-protective layer or membrane. As is known in the art, severalmembranes can be employed to protect the roofing system fromenvironmental exposure, particularly environmental moisture in the formof rain or snow. Useful protective membranes include polymericmembranes. Useful polymeric membranes include both thermoplastic andthermoset materials. For example, and as is known in the art, membraneprepared from poly(ethylene-co-propylene-co-diene) terpolymer rubber orpoly(ethylene-co-propylene) copolymer rubber can be used. Roofingmembranes made from these materials are well known in the art asdescribed in U.S. Pat. Nos. 6,632,509, 6,615,892, 5,700,538, 5703,154,5,804,661, 5,854,327, 5,093,206, and 5,468,550, which are incorporatedherein by reference. Other useful polymeric membranes include those madefrom various thermoplastic polymers or polymer composites. For example,thermoplastic olefin (i.e., TPO), thermoplastic vulcanizate (i.e., TPV),or polyvinylchloride (PVC) materials can be used. The use of thesematerials for roofing membranes is known in the art as described in U.S.Pat. Nos. 6,502,360, 6,743,864, 6,543,199, 5,725,711, 5,516,829,5,512,118, and 5,486,249, which are incorporated herein by reference. Inone or more embodiments, the membranes include those defined by ASTMD4637-03 and/or ASTM D6878-03.

Still in other embodiments, the protective membrane can includebituminous or asphalt membranes. In one embodiment, these asphaltmembranes derive from asphalt sheeting that is applied to the roof.These asphalt roofing membranes are known in the art as described inU.S. Pat. Nos. 6,579,921, 6,110,846, and 6,764,733, which areincorporated herein by reference. In other embodiments, the protectivemembrane can derive from the application of hot asphalt to the roof.

Other layers or elements of the roofing systems are not excluded by thepractice of this invention. For example, and as is known in the art,another layer of material can be applied on top of the protectivemembrane. Often these materials are applied to protect the protectivemembranes from exposure to electromagnetic radiation, particularly thatradiation in the form of UV light. In certain instances, ballastmaterial is applied over the protective membrane. In many instances,this ballast material simply includes aggregate in the form of rock,stone, or gravel; U.S. Pat. No. 6,487,830, is incorporated herein inthis regard.

The high density boards are also advantageously useful in re-roofsituations. In other words, and as is known in the art, an existing roofcan be re-roofed without the need to remove one or more of the existinglayers of the existing roof system. Indeed, a secondary roofing systemcan be applied directly over the existing roofing system. In theseinstances, it is advantageous to apply a “re-coverboard” over theexisting roof before application of another protective membrane. Incertain instances, a second layer of insulation (i.e., a recoverinsulation layer) may also be applied. The additional layer ofinsulation can be applied above or below the re-coverboard, andtherefore the protective membrane is either applied to the re-coverboardor the recover insulation layer. The high-density boards of thisinvention are advantageously applied in re-roofing situations as arecovery board.

For example, one embodiment is shown in FIG. 4, which includes anoriginal roofing system 50 and a re-roof system 51. In a mannerconsistent with that described above, existing roof 50 includes roofdeck 52, insulation layer 54, protective membrane 56, and ballastmaterial 58. Disposed on existing roof 50 is re-roof system 51, whichincludes high density re-coverboard 60, recover protective membrane 64,and ballast material 68. As noted above, high density re-coverboard 60is consistent with the high density boards described hereinabove withrespect to the new roof construction. The nature of this high densityboard advantageously allows it to be used as a re-coverboard. That is,re-coverboard 60 can be applied directly to an existing roof. The robustnature of re-coverboard 60 advantageously allows it to be applieddirectly to material such as ballast material 58.

In other embodiments, the re-coverboard 60 of this embodiment can beapplied directly to an existing roofing membrane. For example, and asshown in FIG. 5, re-coverboard 60 and protective membrane 64 can form are-roof system 51 on top of an existing roofing system 53, whichincludes existing roof deck 52, existing insulation layer 54, andexisting protective membrane 56.

In another embodiment, a composite construction board is provided. Inone embodiment, this composite board can advantageously be employed inthe manufacture of new construction roofing systems. In otherembodiments, the composite boards can advantageously be employed inre-roof situations. In general, the composite boards include one or morehigh density layers and one or more low density layers. They may alsooptionally include one or more facers or one or more reinforcing layerssuch as reinforcing scrims. The positioning of the various layers andfacers can advantageously be varied based upon the intended use orproperties that are desired.

One embodiment of the composite construction board is shown in FIG. 6. Acomposite board 80 includes high density layer 82, low density layer 84positioned underneath high density layer 82, and an optional facer 86.The positions of high density layer 82 and low density layer 84 mayoptionally be reversed. That is, rather than the configuration ofcomposite board 80 shown in FIG. 6, low density layer 84, as shown inFIG. 6A, can instead be positioned above high density layer 82.

Furthermore, additional facers may optionally be positioned between highdensity layer 82 and low density layer 84 and/or optionally bepositioned on the side of composite board 80 opposite optional facer 86.For example, as shown in FIG. 6B, composite board 80 includes anoptional facer 87 positioned between high density layer 82 and lowdensity layer 84, and another optional facer 88 positioned on the sideof composite board 80 opposite optional facer 86. Furthermore, compositeboard 80 can also be configured to include an optional reinforcing layerpositioned between two or more of the various layers. For example, asshown in FIG. 6C, a fiberglass mat 89 is positioned between two optionalfacers 87, 87′ which are positioned between high density layer 82 andlow density layer 84.

Additionally, composite board 80 can be constructed of a plurality ofalternating high density layers and low density layers. For example,composite board 80 may include four layers, where each layer alternatesbetween high density and low density layers. Furthermore, compositeboard 80 could be constructed of three alternating layers where a highdensity layer is sandwiched between two low density layers, or where alow density layer is sandwiched between two high density layers. Eitherway, like the other embodiments discussed above, composite board 80includes at least one high density layer 82 and at least one low densitylayer 84. Moreover, these layers can interface with one another, orfacers can be provided therebetween.

As with the high density construction boards of the first embodiment,high density layer 82 of composite board 80 may be characterized byhaving a density that is greater than 2.5 pounds per cubic foot, inother embodiments greater than 3.0 pounds per cubic foot, and still inother embodiments greater than 3.5 pounds per cubic foot; on the otherhand, the density of high density layer 82 may be less than 20 poundsper cubic foot, in other embodiments less than 10 pounds per cubic foot,and still in other embodiments less than 6 pounds per cubic foot. Lowdensity layer 84 can be characterized by having a foam density that isless than 2.5 pounds per cubic foot, in other embodiments less than 2.0pounds per cubic foot, in other embodiments less than 1.9 pounds percubic foot, and still in other embodiments less than 1.8 pounds percubic foot. In one or more embodiments, these polyurethane orpolyisocyanurate insulation layers may likewise be characterized byhaving a density that is greater than 1.50 pounds per cubic foot andoptionally greater than 1.55 pounds per cubic foot.

In one or more embodiments, high density layer 82 and low density layer84 are cellular in nature. In other words, these layers arecharacterized by an interconnected network of solid struts or platesthat form the edges and faces of cells. In one or more embodiments, thecellular material comprises polyisocyanurate or polyurethane.

When present, the optional facers (e.g., 86, 87, 88) can be formed froma variety of materials. Exemplary facer materials include aluminum foil,cellulosic fibers, reinforced cellulosic fibers, craft paper, coatedglass fiber mats, uncoated glass fiber mats, chopped glass, andcombinations thereof. Useful facer materials are known as described inU.S. Pat. Nos. 6,774,071, 6,355,701, RE 36674, U.S. Pat. Nos. 6,044,604,and 5,891,563, which are incorporated herein by reference. The thicknessof the facer material may vary; for example, it may be from about 0.010to about 0.100 or in other embodiments from about 0.015 to about 0.050inches thick. The facer materials can also include more robust or rigidmaterials such as fiber board, perlite board, or gypsum board. Thethickness of the rigid facer can vary; for example, the thickness of therigid facer can be from about 0.20 to about 1.50 inches, or in otherembodiments from about 0.25 to about 1.00 inches. When present, theoptional reinforcing layers can include a variety of materials. In oneor more embodiments, fiber scrims or mats can be employed. These matsand scrims may include woven and non-woven constructions. The fibers mayinclude fiberglass or synthetic materials such as polyethylene or nylon.

In one or more embodiments, high density layer 82 and low density layer84 comprise the same or similar material. As a result, there is littleinterfacial tension between the layers, which provides an advantageousstrength. In one or more embodiments, high density layer 82 and lowdensity layer 84 are integral with one another as a result of themanufacture and process. In other words, the composite board 80 can bemanufactured by forming low-density layer 84 on top of high densitylayer 82, and the optional facer 86 can thereafter be selectivelyapplied to low density layer 84 (FIG. 6) and/or high density layer 82(FIG. 6A).

In one or more embodiments, high density layer 82 and low density layer84 can be prepared by employing techniques known in the art for theproduction of cellular polyurethane or polyisocyanurate constructionboards. As noted above, the methods are known in the art as disclosed inU.S. Pat. Nos. 6,117,375, 6,044,604, 5,891,563, 5,573,092, U.S.Publication Nos. 2004/01099832003/0082365, 2003/0153656, 2003/0032351,and 2002/0013379, as well as U.S. Ser. Nos. 10/640,895, 10/925,654, and10/632,343 which are incorporated herein by reference.

In one embodiment, the high density cellular body is first formed usingtechniques described above. In one particular embodiment, a facer ispositioned above and below the high density layer. Following themanufacture of this high density board, a low density layer is formedthereon (i.e., the low density layer is formed on one of the facerspositioned on the high density layer) using techniques known in the art.In one particular embodiment, a facer can then be positioned on top ofthe low density layer (i.e., on the planar surface of the low densitylayer that is opposite to the high density layer). In one or moreembodiments, this manufacturing technique can occur within a continuousoperation or production line.

In other embodiments, a high density cellular body or layer can beformed with optional facers. In a second manufacturing step, a lowdensity layer or cellular body can be formed with optional facers. Thehigh density layer (with optional facers) and low density layer (withoptional facers) can be adhered together to form the compositestructure. Optionally, a reinforcement can be positioned therebetween.Conventional adhesives may be employed to adhere the boards to oneanother. In one or more embodiments, the adhesive may include a one-partor two-part polyurethane or polyisocyanurate adhesive. In otherembodiments, a hot-melt adhesive may be employed. Exemplary hot-meltadhesives include polyolefin and polydiolefin-based hot-melt adhesives.

The composite boards can be sized to a variety of dimensions. Ingeneral, composite boards 80 are planar in nature and, as shown in FIG.6, can be characterized by including a length 90, a width 91, and aheight or thickness 92. Because the composite boards are advantageouslyemployed in the construction industry, they may advantageously be sizedto a four foot width and eight foot length (i.e., 4′×8′), other usefulsizes may include 4′×10 and 4′×4′. As for the overall thickness of thecomposite board, the respective thicknesses of the high-density layersand low-density layers can vary and therefore the overall thickness canvary. Likewise, the thickness of the facer employed, if any, willlikewise contribute to the overall thickness of the composite board. Inany event, the thickness of the composite boards of one or moreembodiments can advantageously be from about 1.0 to about 6.0 inches, orin other embodiments from about 1.5 to about 5.0 inches, or in otherembodiments from about 2.0 to about 4.5 inches. In certain embodiments,the thickness of the high-density layer can vary from about 0.5 to about2.0 inches, in other embodiments from about 0.5 to 1.0 inches, and stillin other embodiments from about 0.50 to about 0.75 inches. Thelow-density layer, in one or more embodiments, can also vary from about0.5 to about 4.0 inches, and in other embodiments from about 1.0 toabout 4.0 inches, and still in other embodiments from about 2.0 to about4.0 inches.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES Experiment 1

A 4′×8′×0.75″ high-density cellular body was manufactured withcellulosic facers on the upper and lower surfaces to form a high-densityconstruction board in accordance with this invention. The cellular bodywas characterized by a foam density of 7.5 pounds per cubic foot. Thecompressive strength of the board (per ASTM 1620) was 42.1 pounds persquare inch.

Experiment 2

A 4′×8′×0.75″ high density cellular body was manufactured withcellulosic facers on the upper and lower surfaces to form a high densityconstruction board in accordance with this invention. The cellular bodywas characterized by a foam density of 12 pounds per cubic foot. Thisboard was tested according to UL 790 for fire spread. Specifically, theboard was mechanically attached to a 60 mil low slope, flame retardantEPDM membrane and positioned on top of a 3″ standard low-density board.Pursuant to this test, the fire spread was a maximum of 3′11″ with alateral spread no closer than 6 inches from the edges at a 0.5:12 slope.As those skilled in the art will appreciate, a pass requires less than6′ flame spread, and the front and lateral flame spread is permittedonly along one edge.

Experiment 3

Using a similar board to that employed in Experiment 2, the UL 790 testwas performed with a 45 mil standard EPDM membrane in lieu of the 60 milmembrane. The flame spread was 4′ 6″ of frontal flame spread with nolateral flame spread closer than 4″ from the edges.

Experiment 4

A high density board similar to that in Experiment 2 was analyzed foruplift performance. The board was mechanically attached to a 45 milstandard EPDM membrane using 16 fasteners and plates per 4′×8′ board.Failure occurred at 41 seconds into 165 pounds per square foot. When thefastener pattern was reduced to 10 fasteners end plates per 4′×8′ board,failure occurred at 34 seconds into 105 pounds per square foot.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

1. A covered roof comprising: (a) a roof deck; (b) an insulation boardincluding a polyurethane, a polyisocyanurate, or a mix of polyurethaneand polyisocyanurate cellular structure, said insulation board having adensity that is less than 2.5 pounds per cubic foot, and said insulationboard having a first planar surface and a second planar surface, saidfirst planar surface and said second planar surface each having a facerpositioned adjacent thereto; and (c) a coverboard including apolyurethane, a polyisocyanurate, or a mix of polyurethane andpolyisocyanurate cellular structure, said coverboard having a densitygreater than about 2.5 pounds per cubic foot and less than 6 pounds percubic foot, an iso index of at least 175, and a first planar surface anda second planar surface, said first planar surface and said secondplanar surface each having a facer positioned adjacent thereto.
 2. Ahigh density construction board comprising: a cellular body having afirst planar surface and a second planar surface, a first facer adjacentsaid first planar surface and a second facer adjacent said second planarsurface, wherein said cellular body includes a polyurethane, apolyisocyanurate, or a mix of polyurethane and polyisocyanurate and hasa density greater than about 2.5 pounds per cubic foot and less than 6pounds per cubic foot, and wherein said first facer and said secondfacer are formed from materials selected from the group consisting ofcoated glass fiber mats, uncoated glass fiber mats, chopped glass, andcombinations thereof.
 3. A method comprising: (a) applying a coverboardto a roof, wherein the coverboard includes a polyurethane, apolyisocyanurate, or a mix of polyurethane and polyisocyanurate cellularstructure, said re-coverboard having a density that is greater thanabout 2.5 pounds per cubic foot and less than 6 pounds per cubic foot,an iso index of at least 175, and a first planar surface and a secondplanar surface, said first planar surface and said second planar surfacehaving a facer positioned adjacent thereto; and (b) applying aninsulation board to said roof, said insulation board including apolyurethane, a polyisocyanurate, or a mix of polyurethane andpolyisocyanurate cellular structure, said re-insulation board having adensity that is less than 2.5 pounds per cubic foot.
 4. A covered roofcomprising: (a) a roof deck; and (b) a high density construction boardcomprising a cellular body having a first planar surface and a secondplanar surface, a first facer adjacent said first planar surface and asecond facer adjacent said second planar surface, wherein said cellularbody includes a polyurethane, a polyisocyanurate, or a mix ofpolyurethane and polyisocyanurate and has a density greater than about2.5 pounds per cubic foot and less than 6 pounds per cubic foot, andwherein said first facer and said second facer are formed from materialsselected from the group consisting of coated glass fiber mats, uncoatedglass fiber mats, chopped glass, and combinations thereof.
 5. A methodof covering a roof comprising: applying a high density constructionboard to the roof, the high density construction board comprising acellular body having a first planar surface and a second planar surface,a first facer adjacent said first planar surface and a second faceradjacent said second planar surface, wherein said cellular body includesa polyurethane, a polyisocyanurate, or a mix of polyurethane andpolyisocyanurate and has a density greater than about 2.5 pounds percubic foot and less than 6 pounds per cubic foot, and wherein said firstfacer and said second facer are formed from materials selected from thegroup consisting of coated glass fiber mats, uncoated glass fiber mats,chopped glass, and combinations thereof.